I am thinking of AI generated post after reading yours.

About Bitcoin 21M bitcoin cap, you can read.
How is the 21 Million Bitcoin Cap Defined and Enforced?

If you want to have questions about what will happen after 21M bitcoins mined, read next ones.
Can Bitcoin's Hard Cap of 21 Million Be Changed?
What Will Happen to Bitcoin After All 21 Million are Mined?

Don't skip a first topic that is necessary to understand two other topics.